1. Field of the Invention
The present invention relates to a polymer compound having improved line edge roughness, resolution, adhesiveness to a substrate, thermal stability and the like as a result of inducing uniform distribution of acid, and a chemically amplified resist composition comprising the polymer compound. More particularly, the invention relates to a novel polymer compound which can be used in the production of a resist useful for microprocessing using various radiations far-ultraviolet radiation such as KrF excimer laser or ArF excimer laser, X-radiation such as synchrotron radiation, or charged particle radiation such as electron beam, and a resist composition comprising the polymer compound.
2. Description of the Related Art
Recently, as the semiconductor industry is undergoing a transition to technologies involving line widths of 50 nanometers or less, newer and more advanced lithographic technologies are anticipated to emerge. Although the technology of extreme ultraviolet (EUV) lithography may serve as one of those important technologies capable of patterning in such extreme ranges of line width, the technology of realizing a pattern with a line width of 32 nanometers or less must be a very elaborating operation. The 193-nm lithographic technology can be said to be an important means for realizing the technologies involving line widths around 32 nm in the future, and such technologies can be made possible if the numerical aperture (NA) is increased. According to Rayleigh's Equation, when the refractive index of an immersion fluid or immersion resist is increased, the numerical aperture can be increased as shown in the equation below, and at the same time, the resolution can also be increased. An increase in the refractive index may also bring about an increase in the DOF.R=(K1·λ)/(NA),NA=n sin θwherein R=resolution, λ=wavelength, NA=numerical aperture, n=refractive index, and θ=incident angle.
There is an on-going demand for new resist materials for the purpose of improvements in the properties such as resolution, sensitivity, refractive index and line edge roughness. The refractive index of the currently used resists is in general about 1.65, but the refractive index has been increased to 1.75 or higher by introducing elements such as sulfur to polymers, and resist technologies exhibiting faster sensitivity have been reported. However, these results are somewhat not very satisfactory in the realization of semiconductor integrated circuits requiring further micronization, and in some cases, there also occurs a problem of the photospeed being slow.
In the case of a polymer used as the main raw material of resist, the polymer should have light absorption at the minimum level at the exposure wavelength. In addition to the resist for EUV, the chemically amplified resists which have been conventionally used for ArF excimer laser are in most cases formed from acrylic polymers as the main material, but the acrylic polymers have a disadvantage that the resistance to dry plasma etch is low due to large quantities of oxygen atoms present in the polymer. It is disadvantageous because if the etch resistance is low, the thickness of the resist pattern should be increased to complement for the low resistance, and as the thickness of the pattern is increased, the probability for the pattern to stand safely on the substrate without collapsing becomes lower.
In order to overcome such disadvantages, resins containing many alicyclic olefin groups have been developed as the polymer to be used in the resists for ArF excimer laser. For example, a (meth)acrylate polymer containing an isobornyl group or an adamantanyl group, an olefin polymer purely composed of a norbornene derivative, a maleic anhydride-cycloolefin polymer, and the like may be mentioned.
The (meth)acrylate polymer may be exemplified by the polymer containing an alicyclic functional group, which was published in SPIE 2724:334 (1996), while the maleic anhydride-cycloolefin polymer may be exemplified by the polymer published in SPIE 2724:355 (1996). The case of the (meth)acrylate polymer has less light absorption, but has a disadvantage of having poor etch resistance compared to aromatic compounds. The maleic anhydride-cycloolefin polymer has excellent etch resistance compared to (meth)acrylate polymers, but has a disadvantage that the polymer absorbs too much light in the ArF excimer laser region so that the perpendicularity of the pattern is deteriorated. Furthermore, maleic anhydride monomers have a disadvantage that the monomers undergo hydrolysis reaction due to the moisture in the atmosphere, and thus have poor storage stability when prepared into a resist and put under storage. On the other hand, polymerization of pure olefin derivatives have disadvantages that metallic catalysts should be used, and that the polymerized resins are so hard that the resins do not show excellent properties as resist materials.
In order to supplement these disadvantages described above, the recent trend is focused on the use of more advanced forms of (meth)acrylate copolymers in the resist compositions. In these polymers, alicyclic olefins having more carbon atoms are introduced into the main chain so as to further enhance the etch resistance compared to the polymers using (meth)acrylic derivatives of the early times, and acid-labile moieties do not all vaporize during soft baking, but remain in an oily state in the resist film and tend to facilitate the flow of the acid generated by a photoacid generator during exposure, to thereby improve the patterning properties. Examples of such copolymers include those described in Korean Unexamined Patent Application Nos. 10-2006-7002354 and 10-2004-0080060, Japanese Unexamined Patent Application Publication No. 2002-293840, and the like.